Very Sad Fish Massacre

This is a discussion on Very Sad Fish Massacre within the Freshwater and Tropical Fish forums, part of the Freshwater Fish and Aquariums category; -->
I do see some issues, though not saying these were the actual cause. But combined, may have contributed. I'll explain.
First, I would not ...

I do see some issues, though not saying these were the actual cause. But combined, may have contributed. I'll explain.

First, I would not use baking soda (sodium bicarbonate). Stanley Weitzman, who probably knows more about characins than anyone alive, has written that this is not a good substance for maintaining a pH balance. He says, sodium bicarbonate has no effective buffer action and cannot stabilize pH in the face of additional acidic waste products. And continual use will cause the sodium ions to reach intolerable levels for fish.

To the nitrates, any level above 20ppm is now believed to be detrimental to most tropical fish long term. Many have written that nitrates up to even 400ppm is not much of an issue, but the scientific data does not support this thinking. I would have to dig into my research to find the specific information, but this should make sense when one realizes that most of the fish we maintain in aquaria occur in water with nitrates so low they usually cannot even be measured. And excess nitrogen in any form, be it ammonia, nitrite, nitrate or nitrogen gas, is detrimental. Even ammonium which is basically harmless is rapidly assimilated by plants. But allowing nitrates to increase to the levels you mention is more than the plants can handle, if they are present.

I would not expect the rapid lowering of nitrates to cause fish deaths, but the elevated levels clearly, in my view, have weakened the fish so this may be one factor in the equation. The pH plays into this; at an acidic pH, ammonia changes to ammonium. But as soon as the pH rises above 7, the ammonium changes back to highly toxic ammonia, and this shock could easily kill some fish. As the pH readings are not absolute, this could be part of the problem. When an aquarium has gone without more significant water changes, it is much safer to change less water and do it more frequently in order to bring the biology back to safe levels.

Which brings me to the water changes. Weekly is the absolute minimum, especially in tanks that are overstocked as you mention. Fish are better able to tolerate gradual changes whether worsening or improving, but a sudden change either way may affect them significantly, even causing death. Not knowing what fish in what sized tank, I can't suggest adequate water changes but assuming there are no plants, half the tank every week is advisable once it is back in balance; getting there i would do more frequent changes with less volume, gradually building up. Even nitrates and pH cannot be used as a method of determining water changes, as some wrongly think. There is all the "crud" that is completely unmeasurable and cannot be removed by any amount of filtration. Only a water change removes this, and it is vital. Plants are the only natural "filters" for this, but that is only workable in very minimally-stocked and thickly planted tanks.

To the other parameters mentioned. Hardness would only change via the source water, unless you have something in the aquarium to affect it such as a calcareous substrate. This is where the water supply enters; if there is any chance that your local supplier might adjust the water chemistry, water changes must take this into account.

Temperature of a couple degrees would not of itself kill fish except perhaps for some highly sensitive species. Many of us do water changes and either deliberately or inadvertently lower the temperature by 3-4 degrees. A similar rise is also in itself not problematic.

Reading your comments about substrate brought back one more component to my mind. This is the first time I have changed the tank water since I added new gravel. I recently took out all my old ea gravel and replaced it with CaribSea Instant Aquarium Peace River Gravel and I used the water conditioners they supplied. That has to be the problem (Id like it to be). There could have been all sorts of stuff in that gravel that I took out with a huge water change.

As much as I want the truth, I would also like to think it wasnt just my stupidity in getting the water temp correct that killed them.

Hmm, I have string alage that keeps growing JUST on portions of my Brazillian Pennywort. The roots turn very very dark green and there it will be, not bad but there. So I took out the portions that I could find the string algae but in little areas it is coming back. It has not grown on any other plants at all which seems starnge to me. I have lutea and flamming sword. The Pennywort I have thinned many times really grows. My concern is that the string algae will spread to the other plants. This has been going on for 2 months now. Wouldit be better to just get rid of the Pennywort? The other plants are beautiful and full so wouldn't be a great loss. Input would be appreciated please. Thank you!
Gupgram

I have no measurable ammonia now. I think the high nitrates supports that the ammonia was probably zero yesterday.

I adjusted my pH the day before and my tap comes out at 7.6 so I know it wasnt a huge pH swing.

The particular substrate I used was meant not to be washed because it comes with bacteria, and it came in its own liquid. Does it make sense that that could have raised the hardness? If so, would the hardness have gone up slowly such that the fish survived the addition of the gravel? Now what should I do? How do I measure the hardness ... I guess there si a test?

thank you Byron and CalmWaters for your help with this. It came as such a shock since I didnt feel like I did anything all that different from what I have been doing. The nitrates were definitively higher than normal before this change.

edit: I just read on the CaribSea description that it doesnt change the hardness

I have no measurable ammonia now. I think the high nitrates supports that the ammonia was probably zero yesterday.

I adjusted my pH the day before and my tap comes out at 7.6 so I know it wasnt a huge pH swing.

The particular substrate I used was meant not to be washed because it comes with bacteria, and it came in its own liquid. Does it make sense that that could have raised the hardness? If so, would the hardness have gone up slowly such that the fish survived the addition of the gravel? Now what should I do? How do I measure the hardness ... I guess there si a test?

thank you Byron and CalmWaters for your help with this. It came as such a shock since I didnt feel like I did anything all that different from what I have been doing. The nitrates were definitively higher than normal before this change.

edit: I just read on the CaribSea description that it doesnt change the hardness

I've previously set out the individual issues that may have caused the problem individually or collectively. The main thing is to ensure it does not occur again. And the best way to do that is with regular partial water changes, meaning every week without fail. Nitrates cannot be allowed to rise above 20ppm. You will have to monitor things and if the parameters between tank water and tap water are reasonably close, a water change of 50% weekly will help. If there are significant differences you will have to adjust accordingly. If nitrates still are high with weekly changes, then either the fish load must be reduced or more frequent water changes are necessary. There are aquarists who do water changes every 3 days when it is needed.

I agree, making sure it doesn't happen again is what is important, but I dont think I can really guarantee that without finding the cause.

another possibility that I came across is that the water outgasing could give the fish the bends. If this actually happens, then it sounds quite likely the cause to me. The water was much more gassy than normal; even my pum was getting gas in it. The problem is, doing more frequent water changes isn't going to eliminate this unless I let the water sit.

I'm biased against thinking the nitrates lowered the fish health because it was only a couple weeks and I have friends that go many weeks with nitrates through the roof with no apparent ill affects. Im not saying I dont believe it, but it seems unlikely to me.

On the nitrates, I mentioned earlier that while this is not the likely issue it would likely weaken some fish, and anything that does that is part of a problem because it makes them more susceptible to other issues that otherwise might be fought off.

And I can say that I doubt you will find anyone on this site who does not recommend weekly partial water changes and keeping nitrates below 40ppm and preferably below 20ppm. The long-term effect of both of these cannot be understated. They are in my humble view the foundation of good aquarium management.

so, do I need to let the water sit? Or, would doing a 50% water change have reduced this effect sufficiently?

Quote:

Originally Posted by Byron

And I can say that I doubt you will find anyone on this site who does not recommend weekly partial water changes and keeping nitrates below 40ppm and preferably below 20ppm. The long-term effect of both of these cannot be understated. They are in my humble view the foundation of good aquarium management.

I'm becoming more convinced by the "Gas Bubble Disease" hypothesis. I didnt mention this before, but the fish also had bubbles on their fins. They often get these when I do a water change, but it was worse this time.